<VV> '63 Turbo crank journal clearances

[MarK Durham]

Nick, the sum of problems with the engine as it was torn down indicate the
motor was run hot, which is not hard to do in a Turbo installation.
If you want this motor to last the first thing you need to do is not use
cast rings. They WILL lose tension and compression in the hotter running
environment in a Turbo engine. Use Moly rings, or as a second, do  Chrome
rings. Some do not like chrome rings due to the longer break-in, however, I
used them on my overhaul a couple of years ago and the engine has run
great. I also used Chrome Rings in many hotter running aviation engine
applications with no problems.

While your main bearing clearances are a bit larger than I would like, they
are within worn service limits and you should see no issues doing this. But
if you want the engine to go another 100,000 miles, replace them! Bearings
are cheap! Make sure the oil pump is set up with proper clearances, and
make sure you use a good quality full synthetic oil like the Amsoil 10w40
or Mobil 1 15W50. Keep your rod bearing clearances in new limits. Put the
engine together with a good prelube, or a 50/50 mixture of STP and engine
oil. Break the engine in with good dino oil like Castrol with a ZDDP
additive added, for the first 500 miles, then go to the synthetic.

On the Cam. I do not understand why someone would reuse a cam when it is in
the center of the engine and any small irregularity not seen by the eye can
take out a new lifter because the lobe profile is not perfect like a new
cam. It is poor planning on your part. You have to split the engine to fix
the problem. Reground cams are cheaper than new and work just as well. Do
it right the first time and you will have a engine that will last a long
time.

Mark Durham
Hauser, Idaho
62 Monza coupe Red/Red 4 speed


On Fri, May 30, 2014 at 5:26 PM, Nick R via VirtualVairs <
virtualvairs at corvair.org> wrote:

> Hi
>
> I'm rebuilding my '63 Turbo motor. This is my first Corvair engine rebuild.
> Today we plastigaged  the main bearings for clearances. We did it by the GM
> Service Manual.
>
> Clearances were like this.
>
> Main Journal #1= .003 (has the different style bearing with thrust
> surfaces)
>                        #2= .003
>                        #3= .003
>                        #4= .002
> We are thinking that these numbers are within tolerances and I will not
> benefit from replacing these main  bearings with brand new main bearings. I
> would be interested in hearing from more experienced Corvair engine
> rebuilders out there so that I might draw valuable input from more
> experienced Corvair mechanics.
>
> I will not be torture testing this motor, exceeding red line.
> (Intentionally that is!) I do not want to reassemble it with bearings that
> will cause my motor to grenade when I spool the turbo a bit now and then to
> keep the turbo limber. I understand that missing a gear can undo all of my
> hard work by causing an over rev. No racing.
>
> The problems I found when we opened the engine up were as follows.
>
> 5 of 6 top compression rings were cracked.
>
> #1 piston skirt was cracked across the skirt but intact.
>
> All 6 skirt clearances were about .005
>
> I've sent the heads out for rebuild by an experienced Corvair technician.
>
> I plan on buying new rebored cylinders pistons & cast iron rings .020 over
>
> The camshaft measured out with very little wear. I plan on reusing it with
> new lifters.
>
> Thanks in advance.
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